Probation drug tests are a different ball game in comparison to employment-related drug tests. A person who is placed on court-ordered probation relinquishes many rights, including the right to bear arms, the right to vote, and the right to a fair drug test. There is really no rules on court-ordered drug testing.
Most probation departments, in an effort to keep costs down, will foresake confirmation tests. This can work against the probationeer in a big way. Ceratin OTC meds can result in a false-positive for THC, or any other illicit substance if a cheap screen is used. Without a confirmation test to overrule a screen positive, and if the probationeer isnt lucky enough to be represented by effective counsel, the probationeer can have his/her status revoked and sent back to jail for just simply taking the wrong medications.

Thats why it is urged that if a person is entangled within the legal system, the best thing is to abstain completely from any drug use until the entanglements are over.